There are known aircraft equipped with engine configurations such as Open Rotor (OR) or Turbofan. In these aircraft, potential hazardous events may occur, such as a Propeller Blade Release (PBR) event, i.e., an event where an external blade of an engine comes off and hits the fuselage, or an Uncontained Engine Rotor Failure (UERF) event, i.e., an event where a part of the internal rotor of the engine breaks off, it is released and hits some aircraft structure, i.e., the fuselage, vertical stabilizer, horizontal stabilizer, etc., generating significant damage to these aircraft structures.
Although engine manufacturers are making efforts to reduce the probability of these failure events, experience shows that PBR and UERF events that can lead to catastrophic events continue to occur.
In the case of a Propeller Blade Release event, particular protections are applied in current aircraft, i.e., increased thickness on the aircraft fuselage, however, some studies have been performed in order to assess the carbon fiber composite thickness required by the fuselage in the potential impact area to resist such an event.
In terms of protection for UERF events, there are protections applied in order to minimize the hazards of an engine or an Auxiliary Power Unit (APU) rotor failure. Additionally, a particular protection is applied on fuel tanks if they are located in impact areas, in order to minimize the possibility of fuel cell damage. A shielding made of aluminum or titanium is typically used for these events.
As it is well known, weight is a fundamental aspect in the aeronautic industry, and therefore, there is a trend to use structures of a composite material instead of a metallic material, even for primary structures such as fuselages. The usual composite materials made of carbon fibers, compared to conventional light weight metallic materials, presents a lower impact resistance due to lower out of plane properties and damage tolerance capabilities. Also, no plasticity behavior as on metallic materials is present in composite materials and they are not able to absorb high strain energy amounts when deforming.
Depending on the threat, the most widely spread ballistic composite armors are typically composed of layers of different materials, such as metal, fabrics and ceramics or by sole fabrics of materials with good ballistic performance, also called “dry” fabrics.
Furthermore, as it is well known, the vertical stabilizer often employ a dorsal fin at its forward base which helps to increase the stall angle of the vertical surface and to prevent a phenomenon called rudder lock or rudder reversal.
The dorsal fin comprises a risk of impact area due to the PBR and UERF events. Thus, there is a need for a dorsal fin architecture capable of satisfying the safety requirements and high impact performance. In the present invention, the dorsal fin has a function of shielding the opposite engine from propeller blade release events. Therefore, it shall prevent debris from reaching the opposite engine. Adding thick shielding to structures which are not part of primary load paths is particularly inefficient as these types of structures are light, stiffness driven components.